Author: Andrey Bogdanov
Put numbers into some cells with numbers to form a single connected group of numbered cells; no 2×2 group of cells may be fully numbered. Each bold region must contain at least one number. Each number must be equal the total count of numbered cells in that region. When two numbers are orthogonally adjacent across a region boundary, the numbers must be different.
Grid control: Click at a cell reveals the value chooser. Click at the selected value changes the state of the cell. More details about grid control are at the help page.